What we see day in day out. Golfer sees so and so PGA Pro use a popular putter. Many of these mainline putters have low head weight 335g to 350g tops. Then just slap a large over sized grip on that putter not thinking how it will effect the heft or balance point and wonder why that particular putter is not performing well.
Add in the larger factor eye dominance and how your putting technique works with any single putter design. <---- That's the largest reason why the majority of golfers can not putt worth a crap IMO. And no one even thinks about that factor or addresses it. You see very little written or discussed. But that's another topic, 😉